1. Field of the Invention
The present invention relates to a sewing head driving apparatus for a sewing machine, more particularly to an apparatus which is capable of moving the sewing head between an initial position and a predetermined position which is horizontally apart from the initial position.
2. Description of the Prior Art
In a conventional sewing machine for sewing a workpiece, e.g. a piece of cloth, or embroidering the cloth, a sewing head has been fixed to a certain position which is apart from a table by a predetermined distance. Therefore, when the cloth is set on the table, the sewing head stands in its way, so that operationability of the sewing machine is deteriorated. In view of this defect, it has been proposed to employ a rotary head system which is capable of rotating a head portion of a sewing machine arm to provide a space on a table, in Japanese Patent Laid-open Publication No. 53-56539. Also, it has been proposed in Japanese Utility Model Application No. 54-149467 to employ a sewing head rotating apparatus which is provided with a positioning mechanism for installing the sewing head rotatably on a cylindrical support which is concentric with respect to an upper shaft mounted on an upper frame, and holding the sewing head at a sewing position (working position) or a waiting position rotated from the sewing position about the axis of the upper shaft by a predetermined angle, and which is provided with a driving device for rotating the sewing head.
According to the apparatuses disclosed in the above-described publications, when the cloth is set on the table, the needle driving device does not stand in its way, so that the operationability will be improved a little comparing with the prior apparatus. However, only a needle driving device mounted on the tip end of the sewing head rotates with respect to the table. That is, the main body of the sewing head is retained above a needle plate mounted on the table. Therefore, it is impossible to set the cloth on the table from a position above the needle plate, and impossible to ascertain or watch the set condition of the cloth from that position. In addition, it is not easy to change the needle plate, or adjust the shuttle mechanism or the like. In order to provide an open area above the needle plate, it is necessary to move the sewing head on the horizontal plane, maintaining synchronous relationship between the upper shaft provided for moving the needle vertically and the lower shaft provided for moving the shuttle mechanism. Therefore, with the sewing head simply caused to be movable or rotatable on a horizontal plane, it is impossible to cause the sewing head to maintain the synchronous relationship between the upper shaft and the lower shaft, so that it is impossible to provide a practical apparatus.